The Microwave Spectra, Structure, Dipole Moment, and Chlorine Nuclear Quadrupole Coupling Constants of Methylene Chloride

The microwave spectra of CH2Cl235, CH2Cl35Cl37, CH2Cl237, CDHCl235, CDHCl35Cl37, CD2Cl235, and CD2Cl35Cl37 have been examined and effective moments of inertia have been determined for these seven isotopic species. From these data the effective bond distances and angles were determined as C–Cl distance=1.7724±0.0005A, Cl–C–Cl angle=111°47′±1′, C–H distance=1.068±0.005A (average of all species), or 1.082A (extrapolated to infinite hydrogen mass), and H–C–H angle=112°0′±20′ (average of all species) or 112°58′ (extrapolated to infinite hydrogen mass). The best value for the dipole moment of methylene chloride was found from the Stark splitting to be 1.62±0.02×10−18 esu. The chlorine nuclear quadrupole coupling constants were also determined and their relationship to the structure is discussed.